SilverZuk

I have read bits and pieces on the forum about a piston pump.

Where can I find more about this?

I think my lift pump is tired and I bought one today at NAPA for $76.
Tuesday it started idling at a real low RPM, so much that it has died a few times. I changed the filter, bled the system including the injectors, still has the exact same symptoms.

I figure with 160k and by the feel of the priming lever that the lift pump is tired.

What options do I have to replae the lift pump?
What are the advantages of changing it to another type of pump?
What else could it be besides the lift pump?

This is 93 with minor pump mods.

NeedMoPower

Is it possible the locknut on the idle screw has worked itself loose? I took my factory lift pump off and replaced it with a FASS system. Steady 18psi and is easy to install.

SilverZuk

What is the FASS system?

JD730

FASS is Fuel Air Separator System or something close to that. Expensive IMO.

Some of the guys here, like Wanna have converted to a piston style lift pump for their fuel hungry trucks so they have suffient fuel pressure/flow at high fuel flow rate through the injection pump.

Needs a new pump, similar but not the same as a 2nd gen one(lower psi), new line to the fuel filter, and some massaging of the insulation cover on top of the lifter cover.
Someone here has part number for this conversion.

If the lift pump isn't bad you could be getting air into the system from the suction side of the pump or your idle adjust screw could have worked loose like NeeMoPower said.

Boatnik

I'm no expert on FASS but I believe it stands for Fuel Air Seperator System. It consists of two filter cans and an electric pump. Some guys swear by them, others swear at them.
Cummins makes a low pressure piston style lift pump that fits in place of the diaphram pump. PM Wannadiesel and ask him for the particulars. He wrote me that it is a simple mod. and less trouble than the electric pumps.

Boatnik

MAn, you sure gotta be quick arround here with JD on the job.

wannadiesel

Like Cody said, check your idle screw.

Since you have stock injectors, you don't really need more volume/pressure than a healthy stock pump will put out. The NAPA replacement will be fine, but you can get them for around $40 if you shop around.

If you plan on adding big injectors and going after more than 250 RWHP, then now would be a good time to upgrade to the piston lift pump. It's a simple bolt-in job, and all the part numbers are in the 1st gen FAQ (look under "tech facts" at the top of the page). The pump is identical to the 2nd gen pump except for the pressure spring. Mine puts out 16 psi at idle and I've not been able to suck it down below 8 psi (typical stock pump pressure at idle) under full power. These pressure numbers are after the filter.

brainfade

Hey Silver Zuk,
A heads up on that NAPA pump. If it's the one with the little 'can' on top, held on with a philips screw, take it back. There is a gasket under that can and when the screw vibrates loose (and it will) the pump will suck air and shut you down. If I remember right the pump is made by Federal Mogul, and if your NAPA guy calls thier tech line they will tell him there is a recall on those pumps for that reason. Found this out the hard way about a month ago, and at that time NAPA didn't have any alternative.

SilverZuk

I have changed the fuel filter, changed the lift pump.
The idle screw is still tight.

It still will not idle, so I adjusted the idle up last night.

I primed the system until no air came out at the connection to the injector pump.
I started it and it died. I bled the fuel lines at the injectors several times.
I let it run idle for 4 or 5 minutes and took it for a dirve.
It died before I went 500 feet. I bled the injectors again.
I drove it about 15 miles through country highways.
It drove fine, had normal power, everything normal.

I hopped in this morning and it didn't want to start.
I cycled the manifold heater several times and cranked on it for probably 5 seconds at a time.

I kept adding throttle as I cranked.
After about 7 or 8 times, it finally coughed and fired up sputterring smoke.
I drove it 40 miles to work and it drove fine, had normal power.
I hung it open for 2 or 3 miles, and top speed was the same as always.

So, I am beginning to wonder if I am sucking air some where.
If it is hard to start this evening or tomorrow morning, I will know if there is an air leak, because there is no way after all that bleeding and driving that there should be air in the system.

Any ideas?

wannadiesel

The '92's and '93's don't usually have much trouble with the fuel lines because they are plastic. Perhaps you have a crack in one somewhere? Try (lightly) pressurizing the fuel tank, use a blowgun and a shop rag. That will usually show up an air leak - because it will become a fuel leak.

Your problem does sound like air in the suction side.